We must be friendly to our classmates. And we must listen to our teachers carefully. It's kind of you to help others.
We mustn't talk loudly in class. It's impolite. Don't run in the classroom.
We mustn't eat or drink in class.
【高分句型】
1. We must be friendly to our classmates.
be friendly to...对...友好。
2. It's kind of you to help others.
某人很...去做:It's +形容词+of sb. to do.